For Sandy Crombie, Tuesday should have been a red-letter day. After nearly four decades with Standard Life, the Scottish life insurer he joined from school, he was made chief executive.

“If you have been with an organisation as long as I have, you cannot see it as anything other than a privilege to be asked to lead it,” Crombie said this weekend. “There are 15,000 fantastic people here and 5m policyholders.”

Yet far from celebrating his promotion, Crombie has had an enormously difficult first week — coping with hostile questions about Standard Life’s financial strength and suspicions that the life insurer has given the Financial Services Authority (FSA) a misleading impression about the true scale of its liabilities.

Even Crombie’s own position is under fire. As a life-long employee, he is far from being a new broom. And as head of the group’s investment business and deputy chief executive, Crombie was deeply involved with the decisions that provoked the current crisis.

“I have not had the easiest message to convey, and it’s been against a backdrop of very considerable cynicism,” he said. “I’ll be a tired boy by the time the weekend arrives.”

Like the volcanic rock that provides the foundations of Edinburgh Castle, Standard Life likes to present itself as solid and unchanging.

So it was no surprise that Crombie struggled to explain the drama of a week in which Standard Life parted with its chief executive, had a public row with its regulator, suspended trading in its bonds and abandoned its long-held commitment to mutuality.

This series of mishaps has left Standard Life’s cherished reputation in ruins, and has raised industry doubts about its ability to continue attracting business from the independent financial advisers (IFAs) who are its lifeblood.

The best Crombie can do is to blame a new method of actuarial modelling. “We had to apply this new regime for the first time with new tools. It came up with answers that were different to the ones we expected,” he said.

This is an unsatisfactory explanation for a series of events that have raised serious doubts over Standard Life’s financial strength and undermined confidence in the group’s management. It has been forced to raise £750m of fresh capital and to consider a flotation or even a sale of the business.

Industry rivals are shocked — particularly by the FSA’s decision to appoint independent experts to review Standard Life’s calculation of its liabilities. They say this points to a fundamental breakdown in trust between the life office and its regulator.

The finance director of one large financial-services company said: “If they were coming into my company, I would already have had my P45.

“I cannot think of any other circumstance in which a good, well-run, household company has been obliged to bring in independent experts to look over the shoulders of the people who were already producing the numbers. I would be astonished if there was not a very, very hard hit on actuarial and accounting practices.”